In spite of the significant advances made during the last 10-15 years in understanding allergic disease mechanisms, studies of food allergies have been less productive. A seafood that causes serious allergic reactions is shellfish. Sensitized individuals ingesting shellfish may develop hives, gastrointestinal or respiratory difficulties, and even anaphylaxis. This proposal will investigate, as representative of shellfish allergies, allergic reactions to four common crustaceans (crayfish, lobsters, shrimp and crabs) which are abundantly consumed in the Gulf South region and are the source of significant morbidity. The specific aims of this proposal are to identify and characterize allergic reactions to crustaceans, isolate and analyze the offending allergens, and assess the utility of diagnostic assays in detecting shellfish allergy. To do this, we propose to first identify allergic individuals and characterize their immune response to crustaceans through interview and skin tests, radioallergosorbent test (RAST) and enzyme-linked immunosorbent assay (ELISA) with extracts of crustaceans. Sera from these individuals will be used to develop assays to detect allergens, such as RAST inhibition and crossed radioimmunoelectrophoresis (CRIE). Allergens will be isolated from soluble preparations, and analyzed with standard chromatographic methods. These purified allergens will then be used to reassess the ability of the skin test, RAST, CRIE and ELISA assays to identify individuals allergic to crustaceans. These assays, along with analysis of earlier information, will also be used to assess any shared allergenicity of shellfish allergens. Finally, a small group of individuals with positive immediate hypersensitivity skin tests, defined antigen reactivity, and clinical histories of allergic reactions to shellfish will be challenged in a blinded fachion with the incriminated shellfish to establish the clinical relevance of the data obtained. This study will thus provide data useful for clinical management of patients with seafood allergy while serving as a model to study the mechanisms of other allergic reactions to food.